The parents of the murdered toddler James Bulger have told a parole board hearing that one of his killers, Jon Venables, should not be released after serving his sentence for downloading and distributing indecent images of children.

Ralph Bulger and Denise Fergus said Venables remained a danger to the public. If and when he was released, Venables should be forced to live in "a government secure establishment, such as an army base, which he will not be allowed to leave," said Robin Makin, Mr Bulger's solicitor.

He added: "Any attempt to release Jon Venables would be an experiment that fills Ralph with terror. Ralph fears that an innocent person may be mistaken for Jon Venables and be injured or even killed. If such occurred then Ralph would feel guilty of not having done enough to have prevented such an obvious tragedy."

Both parents were allowed to make representations via live video link to Venables' parole board hearing on Wednesday. Venables, now 30, has applied to be released from jail after being recalled to prison in 2010 and sentenced to two years over a cache of indecent images found on his computer. He had also been posing online as the mother of a young child and discussing child abuse with another paedophile.

He had also been posing online as a mother of a young child and discussing child abuse with another paedophile.

He was 10 when he and his classmate Robert Thompson abducted and murdered two-year-old James in February 1993. They were jailed for life but released on licence with new identities in 2001. A worldwide injunction prevents anyone from revealing their new names or whereabouts.

Makin said: "Jon Venables is a sex offender who has murdered once and made it clear when posing as a mother of a child that an ultimate thrill for him was sexual abuse of a child. Ralph feels that with little prospect of any quality of life Jon Venables might wish to go out with a bang and again sexually assault and murder. The authorities have already experimented with Jon Venables living a lie and it did not work."

Sean Sexton, Fergus's solicitor, said after the hearing: "Denise believes the initial parole board hearing in 2001 was inadequate." She feels the experts failed to take into account a possible sexual motivation for her son's murder – evidence that police deemed inconclusive and which was not included in the trial.

Sexton said: "There was a rush to declare Venables rehabilitated because so much had been invested in him by those supervising him. Denise believes an inconvenient truth was swept under the carpet. Breaches of his licence conditions were not acted upon. Continuing psychiatric supervision, which was a condition of his licence, was abandoned, partly over a dispute over who was to pay for it."

He said Fergus felt she had finally been heard. "For the first time Denise has been given an assurance that the parole board will comprehensively investigate the issues she has raised."

A parole board spokesman said the panel had 14 days to decide whether Venables was fit for release.